Soil quality and sustainability

The world is faced with a dilemma. On the one hand there is a vital need for increased agricultural production to ensure adequate food for this and future generations. On the other hand land is required for several other and conflicting purposes such as buildings, biodiversity and the support of varied plant life, and less is then available to produce food. There is thus huge competition for land, with most potential uses competing for the best quality land. There is also an assumption among many that food is being produced without damaging the soil and without causing any undesirable side effects such as pollution, erosion of the soil and other damage to the environment. This, of course, is not the case and very large areas of land have been rendered unusable for food production over the last 2000 years. It is time to have a new approach to land in which it will be essential to regard almost every piece of land with a view to protecting and managing it very carefully. It is only then that we can view future food production with confidence.

It is important to maintain soil quality. In principle, soil can only be assessed for the particular purposes for which it is to be used, such as suitability of soils for a particular crop, or a particular building programme. Properties of soils ideal for one use may not be the ones useful for another use. Already a great deal is known about the soils of the world. Soil maps at various scales have been made of the soils of most countries. However, very few countries have detailed soil maps at a scale at which one might comfortably say 'we know about our soils'. The developed countries, like USA, Canada, New Zealand and many of those in Europe have maps at reasonably detailed scales. In the developing world, however, soil maps are very patchily distributed and there is a general lack of detail about the soils there and their qualities. Yet if we are going to protect and manage our soils to create a sustainable future for them it is essential that there is a sound knowledge of soils, their properties, quality, use and potential. Urgent steps need to be taken to get this information where it is lacking.

There are several fundamental properties of soils that influence soil quality. A well balanced healthy soil is one that is likely to be the most robust and capable of meeting the requirements for a wide range of uses. Some properties, such as texture, are static and cannot be changed readily. Others are more sensitive to change and it is these that we need to monitor carefully to maintain optimum levels. One of the most important is organic matter because it contributes to many functions, such as stability of soil structure, waterholding capacity, nutrient-supplying power, and is the food for the huge numbers of organisms that live in the soil. Hence it is usually the number one selection in any monitoring of soils, now particularly because of it large potential impact on climate change. Soil acidity, or pH, is another usually essential indicator to be monitored particularly because of the sensitivity of some plants to changes in pH. There has been much discussion on the extent to which soil biodiversity can be monitored but because of its complex nature it cannot be part of any nationwide monitoring, only localised special investigations. As well as some regular nationwide monitoring, there also needs to be monitoring of areas subject to specific problems such as soil erosion as soil pollution. Monitoring is essential as a measure of the health and quality of our soils.